For flat-panel display (hereinafter referred to as FPD) represented by liquid crystal display and organic EL display, a glass substrate is used as a base material for its display panel, however, demand for its substitution by a transparent plastic substrate has been increasing with a view to thickness reduction, weight reduction, improvement of impact resistance as well as adaptability to a roll-to-roll process. Further, it has been attempted to form an organic transistor on a plastic substrate by means of an organic semiconductor, or to form LSI, a Si thin film solar cell, an organic dye-sensitized solar cell and an organic semiconductor solar cell.
Usually, in a case where such an element is formed on a commercially available plastic substrate, the formed element or device, such as a liquid crystal element, an organic EL element, a TFT element, a semiconductor element or a solar cell, is weak against water and oxygen, whereby dark spots or dead pixels are likely to be formed in the display on such a display panel, or a semiconductor device, a solar cell, etc. tend to fail to function properly and tend to be practically useless. Therefore, a gas barrier plastic substrate is required wherein a gas barrier property against steam and oxygen gas is imparted to a plastic substrate. On the other hand, a transparent plastic film having a gas barrier property is likely to be increasingly used, in place of a non-transparent aluminum foil laminate film, in applications as packaging materials for e.g. foods, drugs, electronic materials, electronic components, etc.
As a method to apply a transparent gas barrier layer on a transparent plastic substrate or a transparent plastic film, a PVD method (physical vapor deposition method) and a CVD method (chemical vapor deposition method) are available, but both of them use a vacuum process. Therefore, it is desired to form a gas barrier layer by an economically advantageous coating method which is not a vacuum process and has a higher throughput. However, as a gas barrier polymer to be used in a coating method, polyvinylidene chloride, polyvinyl alcohol, an ethylene/vinyl alcohol copolymer or nylon 6 may, for example, be available, but as compared with a gas barrier layer formed by the PVD method or the CVD method, water and oxygen were more likely to permeate therethrough, and its gas barrier property was low. That is, a coating material having a high gas barrier property is desired.
Further, also for a sealing material for an LED element, a material having a high gas barrier property is likewise desired. Patent Documents 1 and 2 propose a polysiloxane sealing material, and Patent Documents 3 and 4 propose an epoxy resin sealing material. However, their gas barrier property against water and oxygen, heat resistance, heat dissipation property, cracking resistance, and light resistance, particularly UV resistance, are inadequate, and improvements are desired.